While some vendors brave the winter, it seems the profusion of pushcarts sprout with the spring flowers. Some, like long-time peanut vendor Peter Alex of Roxbury, were neighborhood institutions. Others pass through as quickly as their pedal-powered carts can carry them. With the surge in popularity of food trucks in recent years all over the city, we look back at push carts and small stands selling everything from pretzels to produce. Lane Turner and Lisa Tuite